The response of rice and barnyardgrass to clomazone rates (0.22, 0.45, 0.67, 0.9, and 1.12 kg ai/ha) and application timings of preplant incorporated, preemergence (PRE), and delayed PRE (DPRE) were evaluated from 1997 to 1999. Rice bleaching at 14 d after planting (DAP) increased from 5 to 35% as the clomazone rate increased. At 14 and 49 DAP, barnyardgrass control decreased with clomazone at 0.22 kg/ha compared with control at higher rates. Clomazone at 0.22 kg/ha resulted in lower grain yield. Clomazone PRE caused less rice bleaching and lower grain yield compared with DPRE timings. These results indicate that initial bleaching by high clomazone rates may not translate into yield loss. Higher clomazone rates may increase rice yield by improving weed control.
Nomenclature: Clomazone; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; rice, Oryza sativa L., ‘Lemont’, ‘Cypress’.
Additional index words: Application timing, herbicide rate response.
Abbreviations: DAP, days after planting; DPRE, delayed preemergence; PPI, preplant incorporated; PRE, preemergence.